﻿using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Text;
using System.Windows.Forms;

namespace AccessPassword
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        public Form1(string filePath)
            : this()
        {
            txtFilePath.Text = filePath;
        }
        protected override void OnShown(EventArgs e)
        {
            base.OnShown(e);
            if (txtFilePath.Text.Length > 0)
            {
                btnGetPwd.PerformClick();
            }
        }
        private static string GetPassword(string file)
        {
            // 未加密的文件0x42开始至0x61之前的每间隔一字节的数值
            byte[] baseByte = { 0xbe, 0xec, 0x65, 0x9c, 0xfe, 0x28, 0x2b, 0x8a, 0x6c, 0x7b, 0xcd, 0xdf, 0x4f, 0x13, 0xf7, 0xb1, };
            byte flagByte = 0x0c; // 标志 0x62 处的数值
            string password = "";
            try
            {
                FileStream fs = File.OpenRead(file);
                fs.Seek(0x14, SeekOrigin.Begin);
                byte ver = (byte)fs.ReadByte();     // 取得版本, 1为Access2000, 0为Access97
                fs.Seek(0x42, SeekOrigin.Begin);
                byte[] bs = new byte[33];
                if (fs.Read(bs, 0, 33) != 33) return "";
                byte flag = (byte)(bs[32] ^ flagByte);
                for (int i = 0; i < 16; i++)
                {
                    byte b = (byte)(baseByte[i] ^ bs[i * 2]);
                    if (i % 2 == 0 && ver == 1) b ^= flag;  //Access 2000
                    if (b > 0) password += (char)b;
                }

                fs.Dispose();
            }
            catch { }
            return password;
        }

        private void btnGetPwd_Click(object sender, EventArgs e)
        {
            if (File.Exists(txtFilePath.Text))
            {
                try
                {
                    var pwd = GetPassword(txtFilePath.Text);
                    txtPwd.Text = pwd;
                    if (string.IsNullOrEmpty(pwd))
                    {
                        MessageBox.Show("没有密码！", Text);
                    }
                    else
                    {
                        Clipboard.SetText(pwd);
                        //MessageBox.Show("解密成功！", Text);
                    }
                }
                catch (Exception ex)
                {
                    txtPwd.Text = "";
                    MessageBox.Show(ex.Message, Text);
                }
            }
        }

        private void Form1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar == (char)Keys.Escape)
            {
                Close();
            }
        }

        private void Form1_DragEnter(object sender, DragEventArgs e)
        {
            if (e.Data.GetDataPresent(DataFormats.FileDrop))
            {
                var files = (string[])e.Data.GetData(DataFormats.FileDrop);
                if (files.Length > 0)
                {
                    var file = files[0];
                    if (!string.IsNullOrEmpty(file) && File.Exists(file) && (file.ToLower().EndsWith(".mdb") || file.ToLower().EndsWith(".accdb")))
                    {
                        e.Effect = DragDropEffects.Copy;
                        return;
                    }
                }
                e.Effect = DragDropEffects.None;
            }
        }

        private void Form1_DragDrop(object sender, DragEventArgs e)
        {
            var files = (string[])e.Data.GetData(DataFormats.FileDrop);
            if (files.Length > 0)
            {
                var file = files[0];
                if (!string.IsNullOrEmpty(file) && File.Exists(file) && (file.ToLower().EndsWith(".mdb") || file.ToLower().EndsWith(".accdb")))
                {
                    txtFilePath.Text = file;
                    btnGetPwd.PerformClick();
                }
            }
        }

        private void txtFilePath_TextChanged(object sender, EventArgs e)
        {
            toolTip1.SetToolTip(txtFilePath, txtFilePath.Text);
        }

        private void btnOpenFile_Click(object sender, EventArgs e)
        {
            using (OpenFileDialog ofd = new OpenFileDialog())
            {
                ofd.Title = "选择Access数据库文件";
                ofd.Filter = "Access数据库文件(*.mdb;*.accdb)|*.mdb;*.accdb|所有文件(*.*)|*.*";
                ofd.Multiselect = false;
                if (ofd.ShowDialog() == DialogResult.OK)
                {
                    txtFilePath.Text = ofd.FileName;
                    btnGetPwd.PerformClick();
                }
            }
        }
    }
}
